Magnetic tool for retrieving metal objects from a well bore when using coil tubing

ABSTRACT

A magnetic tool for retrieval of metal debris from a well bore particularly adapted for use in coil tubing systems. The tool has a cylindrical body and a plurality of separate magnet assemblies mounted on the tool body. The magnet assemblies are separated by spacers, which define a secondary settling area for the metal objects attracted to the magnetic tool. Each magnet assembly has one or more magnet member encased in a protective sleeve

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of my co-pending applicationSer. No. 10/935,367 filed on Sep. 7, 2004 entitled “Magnetic Tool forRetrieving Metal Objects from a Well Bore,” the full disclosure of whichis incorporated by reference herein. I claim priority of my co-pendingprior application in Venezuela, Application Serial Number 2.004-01414filed on Aug. 31, 2004 entitled “Magnetic Tool for Retrieving MetalObjects from a Well Bore” and in prior U.S. application Ser. No.10/935,367 filed on Sep. 7, 2004 entitled “Magnetic Tool for RetrievingMetal Objects from a Well Bore.”

BACKGROUND OF THE INVENTION

The present invention relates to wellbore tools and more particularly toa magnetic tool for retrieval of metal objects, such as cuttings andother foreign objects that accumulate in the process of perforating ormilling over bridge plugs and other down hole obstructions from awellbore.

As the conventional petroleum resources are becoming more difficult toaccess, the industry started developing means for drilling in moredifficult strata, often in high-pressure or less stable environments. Anew technique called coiled tubing drilling has been used in placeswhere air drilling, mud drilling or fluid drilling are impracticable.Instead of conventional vertical drill string, the coil tubing methoduses a continuous string of concentric coil tubing, which allows fluidcirculation through the tubing. Coil tubing drilling is believed toreduce formation damage as it allows for drilling with less contactbetween a drill string and the surrounding formation. An additionaladvantage of coiled tubing method is related to continuous circulationwhile drilling, which is believed to minimize pressure fluctuations andreduces formation damage.

However, similar to conventional technique, coiled tubing methodgenerates metal cuttings, or shavings, which have to be removed tostimulate fluid circulation. The present invention contemplatesprovision of a magnetic tool for retrieval of metal objects from a wellbore when using coil tubing drilling method.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide anapparatus for retrieval of metal cuttings and other foreign objects froma wellbore, which can be used in a coil tubing system.

It is another object of the present invention to provide a magnetic toolfor retrieving metal objects from a well bore that forms secondarydebris settling area between magnet members.

These and other objects of the present invention are achieved through aprovision of a magnetic tool adapted for retrieval of metal objects froma well bore. The tool has an elongated mandrel, which carries aplurality of spaced-apart magnet assemblies detachably mounted on themandrel. The mandrel has a central opening therethrough to allow fluidcirculation through the tool. Opposite ends of the tool carry connectorsfor securing the tool in a drill string.

Each magnet assembly comprises one or more magnet members encased in aprotective sleeve, which is made from a non-corrosive, structurallystable material. Each magnet assembly has a generally ring-shaped crosssection and end portions having a generally frustoconical configuration.One of the embodiments provides for a magnet member having a unitaryring-shaped configuration. Another embodiment provides for the magnetassemblies having three of more elongated magnet members, which have amagnet encased in a protective sleeve.

Mounted between adjacent magnet assemblies is a tubular spacer, theexterior surface of which forms a secondary settling area for the metalobjects attracted to the magnet assemblies. By strategically spacing themagnet assemblies along the length of the tool body, it is possible tocreate a magnetic field strong enough to cause metal objects to settleon the spacer(s).

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to the drawings, wherein like parts aredesignated by like numerals and wherein

FIG. 1 is a perspective view of the first embodiment of the apparatus ofthe present invention.

FIG. 2 is a perspective view of the mandrel of the magnetic tool offirst embodiment of the present invention.

FIG. 3 is an elevation view of the magnet member of the first embodimentof the apparatus of the present invention.

FIG. 4 is a cross-sectional view of a magnet assembly of the firstembodiment of the apparatus of the present invention taken along lines4-4 of FIG. 3.

FIG. 5 is a detail elevation view of a connector member of the firstembodiment of the apparatus of the present invention.

FIG. 6 is a detail elevation view of a spacer member of the firstembodiment of the apparatus of the present invention.

FIG. 7 is a detail view showing magnetic tool connectors of the secondembodiment of the present invention engaged with top and bottom subs.

FIG. 8 is detail view of a mandrel of the magnet tool of the secondembodiment of the present invention.

FIG. 9 is a detail exploded view showing magnet assemblies and spacermembers of the second embodiment of the present invention; and

FIG. 10 is a detail view of set screw for securing the connector membersto the mandrel.

DETAIL DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the drawings in more detail, numeral 10 designates thewell bore magnetic tool in accordance with the first embodiment of thepresent invention. The tool 10 comprises a tubular cylindrical mandrel,or body 12 having a through opening 14 for admitting circulating fluidinto a wellbore. An upper part 16 of the cylindrical body 12 is providedwith external threads 18. The upper part 16 carries an upper connectormember 20, which threadably detachably engages the upper part 16.

The upper connector member is provided with a central opening 22. Thewalls of the inner opening 22 are provided with two sets of internalthreads. A lower set of internal threads 24 threadably matchinglyengages with the threads 18 of the mandrel 12. An upper set of threads26 is adapted for engagement with other subs forming a drill string (notshown).

A lower part 30 of the mandrel 12 carries a lower connector member 32,which has an enlarged diameter portion 34 and a reduced diameter portion36. The reduced diameter portion 36 is provided with external threads38. The threads 38, similarly to the threads 26 allow connection of thetool 10 to other subs forming the drill string (not shown).

Mounted in a surrounding relationship over the mandrel 12, between theupper connector 20 and the lower connector 32 is a plurality of magnetassemblies 40, 42, and 44. The tool 10 may be provided with one or moremagnet assemblies, depending on the design selected by the manufacturer.The magnet assemblies 40, 42, and 44 are vertically spaced from eachother. The outer surface of each of the magnet members defines a primarysettling area for the metal debris.

One or more tubular spacers 46, 48 (FIG. 6) are positioned on themandrel 12 between the magnet assemblies 40, 42, and 44; the spacers 46,48 form secondary debris settling areas between adjacent magnet members.Due to the predetermined spacing of the magnet assemblies on the mandrel12, the magnetic field created by adjacent magnets overlaps the areas46, 48, causing metal debris to settle on the exterior of the spacers 46and 48, as well.

As can be seen in the drawings, each of the magnet members 40, 42, and44 comprises a body having a generally ring-shaped cross-section with acentral opening therethrough. Each magnet assembly 40, 42, and 44comprises a magnet member 52 completely encased in a metal sleeve 54(FIG. 4). The sleeve 54 may be formed from a non-corrosive structurallystable material, such as for instance stainless steel. Each magnetassembly has a generally tubular configuration. The sleeve 54 has anupper portion 56, which is shaped as a truncated cone.

Each sleeve 54 comprises a lower portion 58, which also has a generallyfrustoconical configuration, such that the upper and lower edges of thesleeve 54 are configured with smaller diameters than the remainingportion of the sleeve body.

An upper edge 60 of each sleeve 54 of the magnet assembly 40 contacts alower edge 62 of the upper connector 20 and matches its reduced diametersize. A lower edge 64 of the magnet assembly 40 contacts and rests on anupper edge 66 of the spacer 40. The external diameter of the spacer bodysubstantially matches the size of the edge 64, supporting the magnetassembly 40 on the mandrel 12.

In a similar manner, an upper edge 68 of the magnet assembly 42 contactsa bottom edge 70 of the spacer 46, while a lower edge 72 contacts andrests on a top edge 74 of the spacer 48. Also similarly, an upper edge78 of the magnet assembly 44 contacts the lower edge 76 of the spacer48, while a lower edge 80 rests on a top edge 82 of the connector 32. Asa result, the magnet assemblies and the spacers are “threaded” on themandrel 12, supporting each other and retaining each other on themandrel 12. The magnet assemblies and the spacers are detachably mountedon the mandrel 12.

The mandrel 12 shown in FIG. 2 illustrates the lower connector member 32unitary formed with the main body of the mandrel 12. If desired, theconnectors 20 and 32 may be secured on the mandrel 12 with set screws90, 92, as shown in FIGS. 1 and 5.

Turning now to FIGS. 7-10, the magnetic tool of the second embodiment ofthe present invention is shown. Similarly to the first embodiment, themagnetic tool of the second embodiment comprises an elongated tubularmandrel 100 having top 102 and bottom 104 threaded portions. A topconnector member 106 and bottom connector member 108 are each providedwith internal threaded portions 110 and 112, respectively, which matchthe threads on the mandrel portions 102 and 104.

A top sub 114 and a bottom sub 116 is secured to the top connector 106and the bottom connector, respectively. Set screws 118 are configuredfor positioning into drilled openings 120 formed in the top connectormember 106 and the bottom connector member 108. The openings 120 aretrilled and tapped to receive the set screws 118. The top sub 114 hasinternal threads 122 for connecting to the drill string (not shown). Thebottom sub 116 has external threads 124 for connection to otherequipment lowered into a well bore (not shown).

The magnet assemblies of the second embodiment are each formed astubular members with a central opening therethrough. In this embodiment,each magnet assembly 130 is made of a plurality of elongated magnetmembers 132, which are secured together to form an open center polygonin cross section. Each magnet member 132 extends longitudinally, in agenerally parallel relationship to the central axis of the tool. Eachmagnet member 132, similarly to the first embodiment, has a magnetencased in a sleeve. Depending on a particular design, the magnetassembly 130 may have three or more magnet members 132.

Mounted between adjacent magnet assemblies 130 is a spacer member 140,which also has a generally ring-shaped cross section. The spacer member140 comprises a plurality of elongated plates 142, which extendlongitudinally in a generally parallel relationship to the central axisof the tool 100. Depending on design, the spacer member 140 may beformed with three or more plates 142.

It is envisioned that the tool 100 may be particularly beneficial in theenvironment, where manufacturing constraints require construction ofmagnet assemblies and spacer members from a plurality of smaller parts.An additional advantage may be that individual magnet assemblies 132 areeasier to replace when damaged or worn. The same may be true forindividual plates 142 of the spacer member 140.

It will be understood that the relative dimensions of the magnetassemblies, spacers and connectors may differ, depending on theparticular design of the magnetic tool 10. If desired, the magnetassemblies may have a vertical dimension of between 3″-6″, while thespacers may have a vertical dimension of 0.5″-2″. The external diameterof the connector members may be between 2″ and 3″, while the diameter ofthe opening 50 may be 1″-1.5″. Of course, other dimensions may besuccessfully employed, when desired.

Many changes and modifications may be made in the design of the presentinvention without departing from the spirit thereof. I, therefore, praythat my rights to the present invention be limited only by the scope ofthe appended claims.

1. An apparatus for retrieving metal objects from a wellbore,comprising: a cylindrical tool body with a central opening therethrough;and a plurality of spaced-apart magnet assemblies configured forpositioning in a surrounding relationship over at least a portion ofsaid tool body, said magnet assemblies defining a primary settling areafor the metal objects; and at least one spacer mounted between adjacentmagnet assemblies, said spacer member defining a secondary settling areafor the metal objects.
 2. The apparatus of claim 1, wherein each of saidmagnet assemblies has a generally ring-shaped cross-section.
 3. Theapparatus of claim 1, wherein each of said magnet assemblies comprises amagnet member encased in a sleeve.
 4. The apparatus of claim 3, whereinsaid sleeve comprises a generally cylindrical main portion and opposingend portions having a generally frustoconical configuration.
 5. Theapparatus of claim 2, wherein each of said magnet assemblies comprises aplurality of elongated magnet members circumferentially disposed aboutthe tool body and extending in a generally parallel relationship to acentral axis of the tool body.
 6. The apparatus of claim 1, wherein saidat least one spacer has a generally tubular configuration.
 7. Theapparatus of claim 6, wherein said at least one spacer comprises aplurality of elongated plates disposed in a circumferential relationshipabout said tool body and extending in a generally parallel relationshipto a central axis of the tool body.
 8. The apparatus of claim 6, whereinan external diameter of said spacer is smaller than an external diameterof each of said magnet assemblies.
 9. The apparatus of claim 1, whereineach of said magnet assemblies and said spacer is detachably mounted onsaid tool body.
 10. The apparatus of claim 1, wherein said tool body isprovided with an upper connector located above said magnet assembliesand a lower connector located below said magnet assemblies, said upperconnector and said lower connector allowing connection of said tool bodyto a drill string lowered into the well bore.
 11. An apparatus forretrieving metal objects from a wellbore, comprising: a cylindrical toolbody with a central opening therethrough; and at least a pair ofspaced-apart magnet assemblies configured for positioning in asurrounding relationship over at least a portion of said tool body, saidmagnet assemblies defining a primary settling area for the metalobjects; and at least one tubular spacer mounted between said magnetassemblies in a surrounding relationship to said tool body, said spacermember defining a secondary settling area for the metal objects.
 12. Theapparatus of claim 11, wherein an external diameter of said spacermember is smaller than an external diameter of each of said magnetassemblies.
 13. The apparatus of claim 11, wherein each of said magnetassemblies comprises a magnet member encased in a sleeve.
 14. Theapparatus of claim 13, wherein said sleeve is formed from anon-corrosive material.
 15. The apparatus of claim 13, wherein saidsleeve comprises a generally cylindrical main portion and opposing endportions having a generally frustoconical configuration.
 16. Theapparatus of claim 11, wherein each of said magnet assemblies and saidspacer is detachably mounted on said tool body.
 17. An apparatus forretrieving metal objects from a wellbore, comprising: a cylindrical toolbody with a central opening therethrough; and at least a pair ofspaced-apart magnet assemblies configured for positioning in asurrounding relationship over at least a portion of said tool body, saidmagnet assemblies defining a primary settling area for the metalobjects, each of said magnet assemblies comprising a plurality ofelongated magnet members secured in a surrounding relationship over atleast a portion of said tool body and extending in a generally parallelrelationship to a central axis of the tool body; and at least onetubular spacer mounted between said magnet assemblies in a surroundingrelationship to said tool body, said spacer member defining a secondarysettling area for the metal objects.
 18. The apparatus of claim 17,wherein said at least one spacer comprises a plurality of elongatedplates disposed in a circumferential relationship about said tool bodyand extending in a generally parallel relationship to a central axis ofthe tool body.